1. Technical Field
This invention relates to a method and apparatus for adjusting the size of an interior volume. More particularly, the invention is related to a method and apparatus providing, adjustable living space, for example within recreational vehicles, military vehicles, and prefabricated housing.
2. Description of the Prior Art
Often, as in the case of recreational vehicles and various military vehicles, an interior space designed for human occupancy must be transported via roadway or similar means. The design of such interiors necessitates a compromise between available interior space and the overall size of the associated vehicle, as generally, the overall size of the vehicle is constrained by factors such as weight, aerodynamic drag, and the width and overhead clearance of the typical roadway.
Several designs proposed in the prior art have sought to avert the negative impacts of this design trade-off with vehicles capable of transforming between two distinct configurations. In these designs, a vehicle typically transforms between a retracted configuration, offering superior road handling but reduced interior space, and a deployed configuration, offering greater interior space but lesser handling characteristics. Typically, the change from the retracted configuration to the deployed configuration involves the assembly, attachment, or erection of an expansion module designed to increase the interior space within the vehicle. An example of such a vehicle is the Eurovan®, manufactured by Volkswagen.
Elements of this approach are seen in many types of vehicles, including those designed strictly for equipment transport. U.S. Pat. No. 4,943,106 to Hunt describes an “equipment trailer having swing-out side extensions provided at each side thereof to enable the overall width of the trailer to be increased when over-width loads are to be carried.” However, Hunt's design is limited to open cargo spaces and does not allow for the expansion of an interior space that protects occupants or cargo from outside elements.
Several solutions have been proposed for the expansion of fully enclosed interior spaces. U.S. Pat. No. 4,960,299 to Steadman describes a “mobile accommodation structure such as a caravan or motor home . . . with at least one foldable extension . . . which can be erected from at least one side wall . . . to enlarge the interior volume enclosed by the mobile structure.” Similar approaches employing foldable or telescoping floors and walls are disclosed in U.S. Pat. No. 2,906,556 to Cantele et al. and U.S. Pat. No. 2,898,143 to Ferrera.
While such approaches provide a larger interior space, the folding and telescoping nature of the floors and walls results in a complicated deployment process that is often labor intensive. Furthermore, the topological transformation in such systems between retracted and deployed configurations prohibits permanent and continued use of the interior space provided by the expansion modules. Furniture, appliances, and similar items must be arranged within the expansion module each time it is deployed.
An approach addressing this shortcoming, most popular with recreational vehicles, is expansion modules outwardly deployed with a linear, sliding motion. FIG. 1 shows a perspective view of a prior art recreational vehicle with an expansion module in a retracted configuration. FIG. 2 shows a perspective view of a prior art recreational vehicle with an expansion module in a deployed configuration. This particular design, detailed in U.S. Pat. No. 6,152,520 to Gardner, incorporates “support arms [that] are connected to the slide out room by a pivoting connection and are connected to the main living area by a connection which both pivots and slides vertically,” providing a level, linear deployment of the slide out room (expansion module). Similar designs are found in U.S. Pat. No. 6,257,638 to Graber and U.S. Pat. No. 5,860,686 to Tiedge.
The large number of moving components and linkages in these designs, however, results in an excessively complicated system with many potential points and modes of failure. The complexity of the deployment mechanism also increases the likelihood that the expansion module jams during deployment. This common shortcoming is evidenced by the extraordinary amount of effort in the prior art devoted to alleviating this difficulty—efforts that have primarily provided only increasingly complicated and expensive systems. Furthermore, the large number of connections, supports, and articulated members between the expansion module and the primary vehicle structure complicates attempts to seal the combined interior space from outside elements, such as rain and wind. Complex linkages also demand substantial clearance between the primary vehicle structure and the expansion module, reducing the distance between the opposing walls or floor and ceiling of the expansion module, and therefore reducing the amount of additional interior space provided. A large clearance between the primary structure and expansion module also creates a visually unappealing interior threshold at the transition between the primary structure and expansion module. Finally, the linear motion of the sliding expansion modules restricts the possible module shapes. Indeed, the great majority of prior art expansion modules of this nature are simple rectangular solids, yielding aesthetically cold and crude interior lines.
What is needed is a simple and effective device that provides a variable amount of interior space within a vehicle without compromising the roadworthiness of the vehicle. The approach should offer convenient and reliable transformation between retracted and deployed configurations with minimal or no manual labor. The transformation should allow for continuous occupation of the interior space provided by the expansion module. The mechanisms enabling the transformation must be simple and reliable.
In particular, the mechanisms should resist jamming of the expansion module during deployment and should facilitate effective sealing of the combined interior space against outside elements. Furthermore, the device should require a minimal amount of clearance between the expansion module and the primary vehicle structure, yielding a minimal reduction in the size of the expansion module. Finally, the approach should provide an aesthetically pleasing combined interior volume.